Synthesis and Characterization of (Ph4P)2[Ni2As4S8], (Me4N)2

(Et4N)2[Mo2O2As2Se7] (III) were synthesized by the hydrothermal reactions of NiCl2/K3AsS3/Ph4PBr, MoO3/K3AsS3/Me4NCl, and MoO3/K3AsSe3/Et4NBr ...
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Inorg. Chem. 1997, 36, 4-9

Articles Synthesis and Characterization of (Ph4P)2[Ni2As4S8], (Me4N)2[Mo2O2As2S7], and (Et4N)2[Mo2O2As2Se7]. New One-Dimensional Polymeric Compounds Containing Thio- and Selenoarsenate Ligands Jun-Hong Chou, Jason A. Hanko, and Mercouri G. Kanatzidis*,† Department of Chemistry and Center for Fundamental Materials Research, Michigan State University, East Lansing, Michigan 48824 ReceiVed December 28, 1995X

The compounds (Ph4P)2[Ni2As4S8] (I), (Me4N)2[Mo2O2As2S7] (II), and (Et4N)2[Mo2O2As2Se7] (III) were synthesized by the hydrothermal reactions of NiCl2/K3AsS3/Ph4PBr, MoO3/K3AsS3/Me4NCl, and MoO3/K3AsSe3/ Et4NBr in a 1:3:4, 1:2:4, and 1:4:6 molar ratio, respectively. The (Ph4P)2[Ni2As4S8] (I) crystallizes in the triclinic space group P1h (No. 2) with a ) 10.613(3) Å, b ) 13.230(2) Å, c ) 9.617(2) Å, R ) 93.53(2)°, β ) 96.69(2)°, γ ) 71.59(2)°, V ) 1272(1) Å3, and Z ) 2. The one-dimensional [Ni2As4S8]n2n- consists of alternating square planar Ni2+ ions and [As4S8]4- ligands. The (Me4N)2[Mo2O2As2S7] (II) crystallizes in the orthorhombic space group Pbca (No. 61) with a ) 18.176(4) Å, b ) 17.010(2) Å, c ) 16.556(7) Å, V ) 5118(4) Å3, and Z ) 4. The [Mo2O2As2S7]n2n- macroanion possesses a one-dimensional chain-like structure consisting of [Mo2O2S2]2+ cores linked by [As2S5]4- ligands. The (Et4N)2[Mo2O2As2Se7] (III) crystallizes in the orthorhombic space group Cmca No. 64) with a ) 15.480(2) Å, b ) 18.506(2) Å, c ) 22.793(2) Å, V ) 6350(1) Å3, and Z ) 4. The [Mo2O2As2Se7]n2n- is isostructural to the anion in II. The solid state optical spectra of these compounds are reported.

Introduction Recently, the hydro(solvo)thermal technique was demonstrated to be a useful synthetic tool toward the synthesis of novel transition and main group metal polychalcogenides that are often inaccessible by traditional solution methods.1-3 In previous communications, this methodology was applied to the R4E+/ Mn+/[AsQ3]3- (E ) P, R ) Ph; E ) N, R ) alkyl, M ) metal; Q ) S, Se) system to synthesize a number of unusual compounds such as [InAs3S7]2-,4 [BiAs6S12]3-,4 [HgAs3S6]-,5a [Hg2As4S9]2-,5a (Me4N)[HgAsSe3],5b (Et4N)[HgAsSe3],5b (Ph4P)2[Hg2As4Se11],5b [Pt(As3S5)2]2-, [Pt3(AsS4)3]3-,6 β-Ag3AsSe3,7 (Me3NH)[Ag3As2Se5],7 K5Ag2As3Se9,7 and KAg3As2S5.7 The most characteristic feature of these compounds is the presence of [AsxQy]n- ligands formed by condensation reactions of a fundamental building unit [AsQ3]3-. The hydrothermal behavior of the R4E+/Mn+/[AsQ3]3- (E ) P, R ) Ph; E ) N, R ) Me, Et; Q ) S, Se; M ) Ni, Mo) systems was explored †

Camille and Dreyfus Teacher Scholar, 1993-1995. Abstract published in AdVance ACS Abstracts, December 1, 1996. (1) (a) Liao, J.-H.; Kanatzidis, M. G. Inorg. Chem. 1992, 31, 431-439. (b) Liao, L. H.; Kanatzidis, M. G. J. Am. Chem. Soc. 1990, 112, 74007402. (c) Huang, S.-P.; Kanatzidis, M. G. J. Am. Chem. Soc. 1992, 114, 5477-5478. (2) (a) Sheldrick, W. S. Z. Anorg. Allg. Chem. 1988, 562, 23-30. (b) Sheldrick, W. S.; Hauser, H.-J. Z. Anorg. Allg. Chem. 1988, 557, 98104. (c) Sheldrick, W. S.; Hauser, H.-J. Z. Anorg. Chem. 1988, 557, 105-110. (3) (a) Wood, P. T.; Pennington, W. T.; Kolis, J. W. Inorg. Chem. 1993, 32, 129-130. (b) Wood, P. T.; Pennington, W. T.; Kolis, J. W. J. Chem. Soc., Chem. Commun. 1993, 25, 235-236. (4) Chou, J.-H.; Kanatzidis, M. G. Inorg. Chem. 1994, 33, 1001-1002. (5) (a) Chou, J.-H.; Kanatzidis, M. G. Chem. Mater. 1995, 7, 5-8. (b) Chou, J.-H.; Kanatzidis, M. G. J. Solid State Chemistry 1996, 123, 115-122. (6) Chou, J.-H.; Kanatzidis, M. G. Inorg. Chem. 1994, 33, 5372-5373. (7) Kanatzidis, M. G.; Chou, J.-H. J. Solid State Chem. 1996, in press. X

S0020-1669(95)01665-X CCC: $14.00

in order to further probe the tendency of the [AsQ3]3- (Q ) S, Se) unit for condensation. There are several examples of early transition metal complexes which contain discrete thioarsenate ligands. One of the early complexes which demonstrated that the thioarsenate anion, [AsS3]3-, could be used as a ligand toward transition metals was Cp′3Ti2O(AsS3) (Cp′ ) η5CH3C5H4).8 Another interesting species was the discrete complex [Mo2O2As4S14]2-, which contains the multidentate [As4S12]4- ligand.8 Of course, the very large number of sulfosalt minerals,9 which contain various [AsxSy]n- ligands in amazingly elaborate binding modes, suggests that these anions would be excellent building blocks for other solid state and coordination compounds. Here we report the successful synthesis of three polymeric compounds using transition metals. These three lowdimensional compounds, (Ph4P)2[Ni2As4S8] (I), (Me4N)2[Mo2O2As2S7] (II), and (Et4N)2[Mo2O2As2Se7] (III), feature higher order thio- and selenoarsenate ligands derived from the condensation of the [AsQ3]3- (Q ) S, Se) anions. Experimental Section Reagents. Chemicals in this work, other than solvents, were used as obtained: NiCl2, 98% purity; MoO3, 99% purity; tetraphenylphosphonium bromide (Ph4PBr), 98% purity; tetramethylammonium chloride. (Me4NCl), 99% purity; tetraethylammonium bromide (Et4NBr), Aldrich Chemical Co. Inc., Milwaukee, WI. Syntheses. All syntheses were carried out under dry nitrogen atmosphere in a Vacuum Atmosphere Dri-Lab glovebox except where specifically mentioned. All compounds have satisfactory elemental analyses. K3AsS3. This material was synthesized by using stoichiometric amounts of alkali metal, arsenic sulfide, and sulfur in liquid ammonia. (8) Zank, G. A.; Rauchfuss, T. B.; Wilson, S. R. J. Am. Chem. Soc. 1984, 106, 7621-7623. (9) Takeuchi, Y.; Sadanaga, R. Z. Kristallogr. 1969, 130, 346-368.

© 1997 American Chemical Society

Polymeric Compounds Containing Arsenate Ligands

Inorganic Chemistry, Vol. 36, No. 1, 1997 5

Table 1. Summary of Crystallographic Data and Structural Analysis for (Ph4P)2[Ni2As4S8] (I), (Me4N)2[Mo2O2As2S7] (II), and (Et4N)2[Mo2O2As2Se7] (III)a formula fw a, Å b, Å c, Å R, deg β, deg γ, deg Z V, Å3 space group color, habit Dcalc, g/cm3 µ, cm-1 2θmax, deg final Rb/Rwc, % a

I

II

III

C48H40P2Ni2As4S8 1351.1 10.612(4) 13.230(2) 9.617(2) 93.53(1) 96.69(2) 71.59(2) 2 1272(1) P1h (No. 2) dark brown, plate 1.69 73.76 45.0 3.7/4.3

C8H24N2Mo2O2As2S7 745.72 18.176(4) 17.010(2) 16.556(7) 90.00 90.00 90.00 4 5118(4) Pbca (No. 61) orange yellow, plate 1.94 40.75 45.0 4.9/6.4

C16H40N2Mo2O2As2Se7 1146.63 15.480(2) 18.506(2) 22.793(2) 90.00 90.00 90.00 4 6350(1) Cmca (No. 64) dark orange, polyhedra 2.33 105.01 50.0 5.4/5.8

Radiation, Mo KR. bR ) ∑(|Fo| - |Fc|)/∑|Fo|.

c

Rw ) {∑w(|Fo| - |Fc|)2/∑w|Fo|2}1/2; w ) (1/σ(Fo2)).

The reaction gives a yellow-brown powder upon evaporation of ammonia. K3AsSe3 was synthesized under similar conditions giving rise to a orange-brown powder. (Ph4P)2[Ni2As4S8] (I). A mixture of 0.025 g (0.2 mmol) of NiCl2, 0.172 g (0.6 mmol) of K3AsS3, and 0.419 g (1 mmol) of Ph4PBr was sealed in a thick-wall Pyrex tube (∼4 mL) under vacuum with 0.3 mL of water. The reaction was carried out at 110 °C for 1 week. The product was isolated by washing away excess starting material and KCl with H2O, methanol, and ether to give 0.105 g (76% yield) of dark brown plate-like crystals. (Me4N)2[Mo2O2As2S7] (II). The reaction of 0.024 g (0.2 mmol) of MoO3, 0.057 g (0.4 mmol) of K3AsS3, and 0.13 g (0.12 mmol) of Me4NCl was prepared as above. The mixture was heated to 110 °C for 1 week. Large yellow chunky crystals were isolated in H2O and washed with methanol and ether (yield ) 88% based on Mo). (Et4N)2[Mo2O2As2Se7] (III). The reaction of 0.014 g (0.1 mmol) of MoO3, 0.172 g (0.4 mmol) of K3AsSe3, and 0.127 g (0.6 mmol) of Et4NBr was prepared as above. The mixture was heated at 110 °C for 3 days. Red-brown crystals were isolated by filtration with methanol and washed with water, methanol, and ether (yield ) 54% based on Mo). Physical Measurements. Optical diffuse reflectance measurements were made at room temperature with a Shimadzu UV-3101PC double beam, double-monochromator spectrophotometer. X-ray Crystallography. The single-crystal X-ray diffraction data of all three compounds were collected with a Rigaku AFC6 diffractometer equipped with a graphite-crystal monochromator at 23 °C. The data were collected with the θ/2θ scan technique. None of the crystals showed any significant intensity decay as judged by three check reflections measured every 150 reflections throughout the data collection. The space groups were determined from systematic absences and intensity statistics. The structures were solved by directed methods of SHELXS-8610a and refined by full-matrix least-squares techniques of TEXSAN10b software package of crystallographic programs. An empirical absorption correction based on ψ-scans was applied to each data set, followed by a DIFABS11 correction to the isotropically refined structures. All non-hydrogen atoms except carbon and nitrogen were refined anisotropically. During the structure refinement it was observed that one of the cations in (II) and (III) respectively was slightly disordered in one of the carbon atoms (C5 for compound (II) and C6 for compound (III)). The occupancy of the C5, C5′ and C6, C6′ was refined to be about 50:50. All calculations were performed on a VAXstation 310076 computer. Complete data collection parameters and details of the structure solution and refinement are given in Table 1. The fractional atomic coordinates, average temperature factors, and (10) (a) Sheldrick, G. M. In Crystallographic Computing 3; Sheldrick, G. M., Kruger, C., Goddard, R., Eds.; Oxford University Press: Oxford, U.K., 1985; pp 175-189. (b) TEXSAN: Single Crystal Structure Analysis Package, Version 5.0; Molecular Structure Corp.: Woodland, TX. (11) Walker, N.; Stuart, D. Acta Crystallogr. 1983, 39A, 158-166.

Table 2. Selected Atomic Coordinates and Estimated Standard Deviations for (Ph4P)2[Ni2As4S8] atom

X

Y

Z

Beqa, Å2

Ni As1 As2 S1 S2 S3 S4 P1 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24

0.50000 0.7376(1) 0.8697(1) 1.0617(3) 0.9398(2) 0.5966(2) 0.6608(2) 1.1891(2) 1.1655(9) 1.041(1) 1.026(1) 1.137(1) 1.261(1) 1.277(1) 1.2995(8) 1.291(1) 1.378(1) 1.466(1) 1.475(1) 1.392(1) 1.0314(8) 0.9817(9) 0.858(1) 0.7849(9) 0.833(1) 0.9561(9) 1.2574(9) 1.258(1) 1.310(1) 1.362(1) 1.360(1) 1.308(1)

0.50000 0.31671(7) 0.46009(7) 0.4380(2) 0.2983(2) 0.3278(2) 0.4927(2) 0.1744(2) 0.0844(6) 0.0827(6) 0.0070(8) -0.0688(8) -0.0669(7) 0.0106(7) 0.2410(6) 0.2701(7) 0.3228(8) 0.3455(8) 0.3176(9) 0.2646(6) 0.2672(6) 0.3635(6) 0.4329(6) 0.4058(7) 0.3100(8) 0.2419(6) 0.0998(6) 0.1549(7) 0.091(1) -0.010(1) -0.0638(8) -0.0106(7)

0.00000 0.1454(1) -0.0314(1) -0.1377(2) 0.0646(2) -0.0452(3) 0.1695(2) 0.4976(2) 0.3592(8) 0.3073(8) 0.207(1) 0.159(1) 0.209(1) 0.308(1) 0.449(1) 0.310(1) 0.276(1) 0.377(2) 0.513(1) 0.547(1) 0.5286(8) 0.4621(8) 0.486(1) 0.579(1) 0.6469(9) 0.6209(9) 0.6525(9) 0.783(1) 0.905(1) 0.897(1) 0.744(1) 0.651(1)

3.4(1) 4.44(6) 4.00(6) 5.1(2) 4.2(1) 5.0(1) 4.6(1) 3.4(1) 3.5(1) 4.0(5) 5.2(7) 6.1(8) 6.0(1) 5.0(1) 4.1(5) 5.2(6) 6.0(7) 6.7(8) 6.9(8) 5.6(7) 3.1(5) 3.6(5) 4.5(6) 4.7(6) 4.7(6) 4.2(5) 4.2(5) 5.8(6) 7.4(8) 7.5(9) 6.6(7) 4.9(6)

a

Beq ) (4/3)[a2B11 + b2B22 + c2B33 + ab(cos γ)B12 + ac(cos β)B13 + bc(cos R)B23]. their estimated standard deviations are given in Tables 2-4.

Results and Discussion Syntheses. (Ph4P)2[NiAs4S8] (I) was prepared by heating NiCl2 with K3AsS3 and Ph4PBr in H2O at 110 °C. It is wellknown in metal polychalcogenide chemistry that different cations can stabilize different structure types.12 Since, conceptually, chalcoarsenate anions are similar to polychalcogenide ligands, we explored several different tetraalkyl ammonium cations. It was observed that upon addition of water the reaction (12) (a) Huang, S.-P.; Kanatzidis, M. G. Inorg. Chem. 1991, 30, 14551466. (b) Kim, K.-W.; Kanatzidis, M. G. J. Am. Chem. Soc. 1992, 114, 4878-4883.

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Table 3. Selected Atomic Coordinates and Estimated Standard Deviations for (Me4N)2[Mo2O2As2S7] atom

X

Y

Z

Beqa, Å2

Mo1 Mo2 As1 As2 S1 S2 S3 S4 S5 S6 S7 O1 O2 N1 N2 C1 C2 C3 C4 C5 C5′ C6 C6′ C7 C8

0.6397(1) 0.6021(1) 0.6469(1) 0.5127(1) 0.4868(3) 0.5847(3) 0.6654(3) 0.5425(3) 0.5672(3) 0.6650(3) 0.5830(3) 0.7135(7) 0.6652(7) 0.299(1) 0.594(1) 0.354(1) 0.292(1) 0.229(1) 0.330(2) 0.511(3) 0.515(2) 0.611(2) 0.620(3) 0.612(2) 0.633(3)

0.7862(1) 0.9237(1) 0.6090(1) 1.0394(1) 0.9961(3) 0.9331(3) 0.8132(3) 0.8728(3) 0.7071(3) 0.6543(3) 0.4969(3) 0.8096(7) 0.9920(7) 0.045(1) 0.235(1) 0.112(1) -0.003(1) 0.074(2) -0.007(2) 0.219(3) 0.231(2) 0.311(3) 0.317(3) 0.188(3) 0.207(2)

0.1285(1) 0.2174(1) 0.0516(1) 0.3516(1) 0.2268(3) 0.3632(3) 0.2640(3) 0.1040(3) 0.0345(3) 0.1768(3) 0.0728(3) 0.0719(7) 0.1887(8) 0.094(1) 0.165(1) 0.107(1) 0.169(1) 0.070(2) 0.028(2) 0.164(3) 0.196(2) 0.134(3) 0.196(4) 0.101(3) 0.235(3)

1.85(7) 1.83(7) 2.5(1) 2.6(1) 3.0(3) 2.4(2) 2.4(2) 2.3(2) 2.7(3) 2.6(3) 2.6(3) 2.5(6) 2.6(7) 2.5(8) 4(1) 3(1) 4(1) 8(2) 6(2) 5(1) 1.5(9) 3(1) 6(1) 12(1) 13(1)

a B ) (4/3)[a2B + b2B + c2B + ab(cos γ)B + ac(cos β)B eq 11 22 33 12 13 + bc(cos R)B23].

Table 4. Selected Atomic Coordinates and Estimated Standard Deviations for (Et4N)2[Mo2O2As2Se7] X

Y

Z

Beqa, Å2

0.3760(2) 0.3943(2) 0.3936(3) 1/ 2 1/ 2 1 /2 0.213(3) 1/ 2 0.151(3) 0.270(3) 0.208(2) 0.222(2) 0.619(3) 0.442(5) 0.428(5) 0.369(3) 0.460(7)

0.2081(2) 0.0806(2) -0.0358(2) 0.3805(3) 0.1607(2) 0.3147(2) 0.0411(2) 0.4995(2) 0.014(1) 0.171(1) 1/ 2 0.229(2) 0.438(2) 0.506(2) 0.359(2) 0.523(2) 0.299(2) 0.231(3) 0.161(4) 0.169(2) 0.225(4)

0.3907(2) 0.3158(2) 0.1936(2) 0.4489(2) 0.3348(1) 0.3959(2) 0.2354(2) 0.4072(2) 0.364(1) 0.456(1) 1 /2 0.654(2) 0.502(2) 0.556(2) 0.506(1) 0.612(2) 0.604(2) 0.712(3) 0.664(3) 0.711(2) 0.589(4)

2.7(2) 2.6(1) 3.6(3) 3.8(3) 3.3(2) 3.8(2) 4.2(2) 3.8(3) 3(2) 4(2) 3.9(9) 4(1) 8(1) 11(1) 4.0(8) 4.7(8) 8(1) 4(2) 6(2) 6(1) 9(1)

atom Mo1 Mo2 As1 As2 Se1 Se2 Se3 Se4 O1 O2 N1 N2 C1 C2 C3 C4 C5 C6 C6′ C7 C8

1/

2

1/

2

1/

2

1/

2

a B ) (4/3)[a2B + b2B + c2B + ab(cos γ)B + ac(cos β)B eq 11 22 33 12 13 + bc(cos R)B23].

mixture immediately gave a black precipitate of NiSx. No other products were observed even after prolonged heating. The same phenomenon was observed when Ph4PBr was used; however, prolonged heating resulted in the formation of dark brown plates of (Ph4P)2[NiAs4S8] as the major product with a small amount (5%) of black NiS precipitate. (Me4N)2[Mo2O2As2S7] (II) was prepared by heating MoO3 with K3AsS3 and Me4NCl in H2O at 130 °C. Again, several other tetraalkylammonium cations were tried and only Et4N+ afforded a crystalline product. However, the poor crystal quality of the Et4N+ salt prohibited further characterization. The (Et4N)2[Mo2O2As2Se7] (III) was prepared by heating MoO3 with K3AsSe3 and Et4NBr in H2O at 110 °C. Reactions with other

A

B

Figure 1. ORTEP representation and labeling scheme of the repeating unit (A) and a long section of a single [Ni2As4S8]n2n- chain (B). Table 5. Selected Distances (Å) and Angles (deg) in (Ph4P)2[Ni2As4S8] with Standard Deviations in Parentheses Ni-S3 As1-S2 As1-S4 As2-S1 S3-Ni-S3 S3-Ni-S4 S2-As1-S3 S3-As1-S4 S1-As2-S2 As2-S1-As2 As1-S3-Ni

2.222(2) 2.303(3) 2.218(2) 2.250(2) 180.00 91.41(9) 104.8(1) 88.51(9) 95.48(9) 90.47(9) 90.69(9)

N1-S4 As1-S3 As2-S1 As2-S2 S3-Ni-S4 S4-Ni-S4 S2-As1-S4 S1-As2-S1 S1-As2-S2 As1-S2-As2 As1-S4-Ni

2.202(2) 2.208(3) 2.314(3) 2.250(2) 88.59(9) 180.00 99.81(9) 89.53(9) 102.5(1) 93.99(9) 90.97(9)

tetraalkylammonium cations, such as triethylmethylammonium13a and tetramethylammonium13b afforded crystalline products. A crystal structure was attempted on the triethylmethylammonium salt and revealed the anion to be isostructural to the [Mo2O2As2Se7]n2n- anion of III. The organic cations, however, showed significant disorder, and a weakly diffracting crystal prevented further structural refinement. Structure of (Ph4P)2[Ni2As4S8]. The [Ni2As4S8]n2n- macroanion has an unusual one-dimensional polymeric structure composed of square planar Ni2+ ions and [As4S8]4- ligands. The [As4S8]4- ligand has not been seen before and is formed by a central core of edge-sharing [AsS3]3- ligands capped by two corner-sharing pyramidal [AsS3]3- units, see Figure 1. The [Ni2As4S8]n2n- chains run along the crystallographic a-axis and are well separated by Ph4P+ cations. The Ni2+ resides on an inversion center with Ni-S distances of 2.202(2) and 2.222(2) Å, respectively. Selected bond distances and angles for (Ph4P)2[Ni2As4S8] are given in Table 5. The average As-S distance and the average S-As-S angles are well within the normal range found in other arsenic/sulfide compounds.14 The unique feature of this compound is the [As4S8]4- ligand, which can be derived from the condensation of four [AsS3]3- units. As discussed earlier,5 the [AsS3]3- unit exhibits facile condensation reactions resulting in higher nuclearity [AsxSy]n- ligands. Remarkably, the [As4S8]4- unit contains a four-membered As2S2 ring with trans connection to the other [AsS3]3- units. In this example of the [AsxSy]n- anion, the [AsS3]3- pyramids share (13) (a) Crystals of (Et3MeN)2[Mo2O2As2Se7] are orthorhombic Cmca (No. 64) with a ) 14.989(7) Å, b ) 18.086(6) Å, c ) 21.125(5) Å, V ) 5746(3) Å3, Z ) 4, Dcalc ) 2.682 g/cm3, µ ) 119.47 cm-1, 2θmax ) 40.0; R/Rw ) 7.5/13.9 %. Single-crystal X-ray diffraction data were collected at -100 °C on a Rigaku AFC6 diffractomer. (b) Hanko, J. A.; Kanatzidis, M. G. Work in progress. (14) (a) Sommer, H.; Hoppe, R. Z. Anorg. Allg. Chem. 1977, 430, 199. (b) Sheldrick, W. S.; Kaub, J. Z. Naturforsch. 1985, 40b, 571-573. (c) Jerome, J. E.; Wood, P. T.; Pennington, W. T.; Kolis, J. W. Inorg. Chem. 1994, 33, 1733-1734.

Polymeric Compounds Containing Arsenate Ligands

Inorganic Chemistry, Vol. 36, No. 1, 1997 7

A

B

Figure 2. ORTEP representation and labeling scheme of the repeating unit (A) and a long section of a single [Mo2O2As2S7]n2n- chain (B).

A

B

Figure 3. ORTEP representation and labeling scheme of the repeating unit (A) and a long section of a single [Mo2O2As2S7]n2n- chain (B).

both corners and edges. A similar four-membered ring in a cis connection is found in [As6S12]6-, which exists in the sulfosalt PbTlAs3S6.15 The [As4S8]4- ligands can also be viewed as the intermolecular condensation product of the [As4S9]6- ligands found in [Hg2As4S9]2-,5 see Scheme 1. The [As4S8]4- represents a new thioarsenate anion. Structure of (R4N)2[Mo2O2As2Q7] (R ) CH3, Q ) S and R ) CH3CH2, Q ) Se). The [Mo2O2As2Q7]n2n- chains of II and III, see Figure 2 and Figure 3, consist of [Mo2O2Q2]2+ cores linked by [As2Q5]4- (Q ) S, Se) ligands forming a onedimensional chain. The [As2Q5]4- ligands are formed by two corner-sharing [AsQ3]3- units. The chains in II and III run along the crystallographic b-axis and are separated by tetramethylammonium cations in II and tetraethylammonium cations in III. The overall conformation of the chains in II and III is (15) Balı´c-Zunı´c, T.; Engel, P. Z. Kristallogr. 1983, 165, 261-269.

Scheme 1

sinusoidal with a period corresponding to the length of the b lattice constant. In II the chains run in-phase, while in III the chains run both in-phase and out-of-phase with respect to each other. The chain in III is situated on a crystallographic mirror plane perpendicular to the a-axis. The [Mo2O2Q2]2+ (Q ) S, Se) core fragment in II and III is well-known in molecular Mo-Q (Q ) S, Se) chemistry; examples include [Mo2O2S2(S2)2]2-,16,17 [Mo2O2S2(S3O2)]2-,18 and [Mo2O2Se2(Se2)2]2-.19 This is the first example in which the [Mo2O2Q2]2+ cores have been incorporated into a polymeric

8 Inorganic Chemistry, Vol. 36, No. 1, 1997

Chou et al.

Table 6. Selected Distances (Å) and Angles (deg) in (Me4N)2[Mo2O2As2S7] with Standard Deviations in Parentheses Mo1-Mo2 Mo1-S4 Mo1-S6 Mo2-S1 Mo2-S3 Mo1-O1 As1-S6 As1-S5 As1-S7 Mo2-Mo1-S3 Mo2-Mo1-S5 Mo2-Mo1-O1 S3-Mo1-S5 S3-Mo1-O1 S4-Mo1-S6 S5-Mo1-S6 S6-Mo1-O1 Mo1-Mo2-S2 Mo1-Mo2-S4 S1-Mo2-S2 S1-Mo2-S4 S2-Mo2-S3 S2-Mo2-O2 S3-Mo2-O2 S5-As1-S6 S6-As1-S7 S1-As2-S7 Mo2-S1-As2 Mo1-S3-Mo2 Mo1-S6-As1

2.848(2) 2.335(5) 2.425(5) 2.435(6) 2.335(5) 1.70(1) 2.236(6) 2.230(6) 2.260(6) 52.4(1) 130.7(1) 106.5(4) 145.9(2) 109.3(8) 141.6(2) 78.7(2) 104.6(4) 126.6(1) 52.4(1) 78.0(2) 80.8(2) 77.9(2) 108.6(4) 108.0(5) 87.4(2) 87.4(2) 104.1(2) 92.5(5) 75.1(2) 89.2(2)

As2-S7 Mo1-S3 Mo1-S5 Mo1-O1 Mo2-S2 Mo2-S4 As2-S1 As2-S2 Mo1-S5-As1 Mo2-Mo1-S4 Mo2-Mo1-S6 S3-Mo1-S4 S3-Mo1-S6 S4-Mo1-S5 S4-Mo1-O1 S5-Mo1-O1 Mo1-Mo2-S1 Mo1-Mo2-S3 Mo1-Mo2-O2 S1-Mo2-S3 S1-Mo1-O2 S2-Mo2-S4 S3-Mo2-S4 S4-Mo2-O2 S5-As1-S7 S1-As2-S2 S2-As2-S7 Mo2-S2-As2 Mo1-S4-Mo2

2.262(6) 2.337(5) 2.442(6) 1.68(1) 2.440(5) 2.334(5) 2.245(6) 2.240(5) 88.9(2) 52.4(1) 129.4(1) 101.1(2) 80.1(2) 80.1(2) 110.9(4) 101.9(5) 130.9(2) 52.5(1) 104.8(4) 144.1(2) 104.7(5) 139.5(2) 101.3(2) 110.0(5) 108.5(2) 86.3(3) 98.3(2) 92.5(2) 75.2(2)

Table 7. Selected Distances (Å) and angles (deg) in [Me4N)2[Mo2O2As2Se7] with Standard Deviations in Parentheses Mo1-Mo2 Mo1-Se2 Mo2-Se1 Mo2-O1 As1-Se4 As2-Se2 Mo2-Mo1-Se1 Mo2-Mo1-Se2 Mo2-Mo1-O2 Se1-Mo1-Se2 Se1-Mo1-O2 Se1-Mo1-Se2 Se2-Mo1-O2 Mo1-Mo2-Se1 Mo1-Mo2-Se3

2.915(6) 2.566(5) 2.465(5) 1.65(3) 2.391(8) 2.371(6) 53.6(1) 130.5(2) 102(1) 78.6(2) 109.3(8) 142.2(3) 106(1) 53.9(2) 130.5(2)

Mo1-Se1 Mo1-O2 Mo2-Se3 As1-Se3 As2-Se4 Se3-Mo2-O1 Mo1-Se1-Mo2 Mo1-Se2-As2 Mo2-Se3-As1 As1-Se4-As2 Se3-As1-Se4 Se2-As2-Se4 Mo1-Mo2-O1 Se1-Mo2-Se3

2.468(5) 1.65(3) 2.572(5) 2.377(6) 2.398(7) 105(1) 72.5(2) 88.9(2) 90.5(2) 97.3(4) 102.6(3) 106.1(3) 103(1) 142.4(3)

framework. With the introduction of the trivalent As atom, the [AsxSy]n- ligand’s potential connectivity is increased, greatly improving the chances of forming a polymeric compound. The Mo-Mo distances of 2.848(2) and 2.915(6) Å in II and III, respectively, are similar to those found in the molecular polychalcogenide compounds.16-19 Selected bond distances and angles for II and III are given in Tables 6 and 7, respectively. There are two different types of Mo-Q distances in II and III. In II the average Mo-S distance, 2.335(5) Å, inside of the [Mo2O2S2]2+ core is significantly shorter than the Mo-S distance, 2.435(5) Å, between the core and the thioarsenate (16) (a) Clegg, W.; Mohan, N.; Mu¨ller, A.; Neumann, A.; Ritter, W.; Sheldrick, G. M. Inorg. Chem. 1980, 19, 2066-2074. (b) Coucouvanis, D.; Koo, S. M. Inorg. Chem. 1989, 28, 2-5. (c) Draganjac, M.; Simhon, E.; Chan, L. T.; Kanatzidis, M. G.; Baenziger, N. C.; Coucouvanis, D. Inorg. Chem. 1982, 21, 3321-3332. (17) Mu¨ller, A.; Ro¨mer, M.; Ro¨mer, C.; Reinsch-Vogell, U.; Bo¨gge, H.; Schimanski, U. Monatsh. Chem. 1985, 116, 711-719. (18) Mu¨ller, A.; Reinsch-Vogell, U.; Krickemeyer, E.; Bo¨gge, H. Angew. Chem., Int. Ed. Engl. 1982, 21, 796-782. (19) Eichhorn, B. W.; Gardner, D. R.; Nichols-Ziebarth, A.; Ahmed, K. J.; Bott, S. G. Inorg. Chem. 1993, 32, 5412-5414.

Figure 4. (A) Optical absorption spectrum of (Ph4P)2[Ni2As4S8]. (B) Optical absorption spectrum of (Me4N)2[Mo2O2As2S7]. (C) Optical absorption spectrum of (Et4N)2[Mo2O2As2Se7].

ligands. In III a similar trend is observed for the Mo-Se distances. The average Mo-Se distance is 2.467(5) Å within the [Mo2O2Se2]2+ core and 2.569(5) Å between the core and the polyselenoarsenate ligand. A comparison of the Mo-Q bond distances of several compounds which contain the [Mo2O2Q2]2+ core is given in Table 8. The Mo-Q distances for the polymeric species II and III compare well with the molecular polychalcogenide counterparts. This trend in alternating Mo-S bond lengths between the [Mo2O2S2]2+ core and the bridging polysulfides is also observed in the molecular species [Mo2S10]2- and to a lesser extent in [Mo2S12]2-.20 This dramatic shortening may be due to the enhanced Modπ-Qpπ bonding interactions in the [Mo2O2Q2]2+ core. This may be attributed to the fact that the monochalcogenides in the core are bridging two Mo5+ centers while the chalcogenides of the ligands are bonded to only one. But with a limited number of examples further work will be needed to confirm this observation. Similar trends were observed in [Mo2O2As4S14]2- 8 (see Table 8). It is noteworthy that in the same paper Rauchfuss et al. describes a cyclic structure for [Mo4O4As4S14]4- where two [As2S5]4- ligands connect two [Mo2O2S2]2+ cores.8 The compounds reported here are the polymeric analogs of (Ph4P)4[Mo4O4As4S14]. The [As2S5]4- unit of II occurs in the sulfosalts PbTlCuAs2S5 (Wallisite),21 PbTlAgAs2S5 (Hatchite),22 (20) Draganjac, M.; Simhon, E.; Chan, L. T.; Kanatzidis, M. G.; Baenzinger, N. C.; Coucouvanis, D. Inorg. Chem. 1982, 21, 3321-3332.

Polymeric Compounds Containing Arsenate Ligands

Inorganic Chemistry, Vol. 36, No. 1, 1997 9

Table 8. Comparison of the Axial and Bridging Bond Distances (Å) and Selected Angles (deg) within Various [Mo2O2Q2]2+ Cores in Discrete and Polymeric Complexesa

Mo1-Mo2 Mo1-O Mo2-O Mo1-Q1 Mo1-Q2 Mo2-Q1 Mo2-Q2 Mo-Q(av) Mo1-Q3 Mo1-Q4 Mo2-Q5 Mo2-Q6 Mo-Q(av) Mo1-Q1-Mo2 Mo1-Q2-Mo2 a

[Mo2O2S6]2-

[Mo2O2As2S7]2-

[Mo2O2As4S14]2-

[Mo2O2Se6]2-

[Mo2O2As2Se7]2-

2.825(2) 1.670(11) 1.680(9) 2.320(4) 2.372(4) 2.330(4) 2.320(4) 2.33(1) 2.392(5) 2.441(5) 2.422(5) 2.382(6) 2.41(1) 74.8(1) 74.9(1)

2.848(2) 1.70(1) 1.68(1) 2.337(5) 2.335(5) 2.335(5) 2.334(5) 2.335(5) 2.442(6) 2.425(5) 2.435(6) 2.440(5) 2.43(1) 75.1(1) 75.2(2)

2.828(3) 1.688(14) 1.718(11) 2.320(5) 2.294(6) 2.301(7) 2.308(4) 2.305(5) 2.441(5) 2.447(8) 2.455(6) 2.448(6) 2.44(2) 75.5(2) 75.8(2)

2.888(2) 1.672(6) 1.702(6) 2.456(1) 2.445(2) 2.453(2) 2.446(2) 2.443(5) 2.538(2) 2.545(2) 2.540(2) 2.544(2) 2.54(1) 72.1(1) 72.4(1)

2.915(6) 1.65(3) 1.65(3) 2.468(5) 2.465(5) 2.466(5) 2.566(5) 2.572(5) 2.56(3) 72.5(2)

Schematic of the common structural fragment with a common labeling scheme is provided at the top of this table.

and Tl2MnAs2S5.23 Examination of the literature for the occurrence of [As2Se5]4- observed in III revealed only one example, Tl2As2Se5.24 These compounds are wide band gap semiconductors. The optical absorption spectrum of (Ph4P)2[NiAs4S8], see Figure 4, spectrum A, exhibits an intense, steep absorption edge, revealing an optical band gap of 2.2 eV. The spectra of (R4N)2[Mo2O2As2Q7] (Q ) S, Se) also show a similar absorption edge with a corresponding band gap at 2.5 and 2.2 eV, see Figure 4, spectra B and C. The intense absorptions are probably due to a chalcogen to metal charge-transfer transition. (21) Takeuchi, Y.; Ohmasa, M. Z. Kristallogr. 1968, 127, 349-365. (22) Marumo, E.; Nowacki, W. Z. Kristallogr. 1967, 125, 249-265. (23) Gostojic, M.; Edenharter, A.; Nowacki, W.; Engel, P. Z. Kristallogr. 1982, 158, 43-51. (24) Kirilenko, V. V.; Samokhov, V. A.; Velikova, N. G.; Shchelokov, R. N.; Medvedev, A. V. Inorg. Mater. 1982, 18, 773.

In conclusion, the [AsQ3]3- anion produces oligomers which act as bridging units to connect known molecular clusters giving new metal/arsenic/chalcogenide chemistry. Three important factors dominate this chemistry: the condensation equilibria among the thio- and selenoarsenate anions, the nature of counterions (templates), and the coordination preferences of the metal ions. Further investigations will explore the existence of other novel [AsxQy]n- anions and the possibility of using them as synthetic building blocks for solid state materials. Acknowledgment. Financial support from the Donors of the Petroleum Research Fund, administered by the American Chemical Society, is gratefully acknowledged. Supporting Information Available: Tables of anisotropic thermal parameters (21 pages). Ordering information is given on any current masthead page. IC951665I